Interventional medical devices, device systems, and fixation components thereof

Abstract

A fixation mechanism of an implantable medical device is formed by a plurality of tines fixedly mounted around a perimeter of a distal end of the device. Each tine may be said to include a first segment fixedly attached to the device, a second segment extending from the first segment, and a third segment, to which the second segment extends. When the device is loaded in a lumen of a delivery tool and a rounded free distal end of each tine engages a sidewall that defines the lumen, to hold the tines in a spring-loaded condition, the first segment of each tine, which has a spring-biased pre-formed curvature, becomes relatively straightened, and the third segment of each tine, which is terminated by the free distal end, extends away from the axis of the device at an acute angle in a range from about 45 degrees to about 75 degrees.

What is claimed is: 
     
       1. An implantable medical device (IMD) including a device body extending along a longitudinal axis from a proximal end to a distal end, an electrode mounted in proximity to the distal end of the device body, and a fixation mechanism comprising a plurality of tines formed from an elastically deformable material, each tine of the plurality of tines being fixedly mounted and spaced from one another around a perimeter of the distal end of the device body, wherein each tine of the plurality of tines comprises:
 a proximal portion being fixedly attached to the device body, wherein the proximal portion is configured to extend from the device body in a first direction, and wherein the proximal portion is configured to define a first pre-formed curvature; and 
 a distal portion comprising:
 a proximal section configured to extend from the first pre-formed curvature of the proximal portion in a second direction along a relatively straight line; 
 a hook section extending from the proximal section, wherein the hook section is configured to define a second pre-formed curvature; and 
 
 a tip section extending from the hook section to a free distal end, 
 wherein, when in a deployed configuration, an intersection between the proximal portion and the distal portion of each tine of the plurality of tines is spaced distally from the distal end of the device body, and 
 wherein the electrode is flush with, or spaced distally from the intersection between the proximal portion and the distal portion by a distance less than or equal to about 2 mm. 
 
     
     
       2. The device of  claim 1 , wherein each tine of the fixation mechanism has a constant thickness of about 0.005 inch and a width no less than about 0.02 inch, and wherein the width of each tine tapers from a greater width in proximity to the device body to a lesser width in proximity to the hook section of the distal portion. 
     
     
       3. The device of  claim 2 , wherein the free distal end of each tine of the fixation mechanism has an enlarged width relative to a remainder of the tip section of the corresponding distal portion. 
     
     
       4. The device of  claim 1 , wherein the first pre-formed curvature of the proximal portion of each tine of the fixation mechanism is defined by a radius, when undeformed, within a range from about 0.06 inch and about 0.08 inch. 
     
     
       5. The device of  claim 1 , wherein the tip section of the distal portion of each tine of the fixation mechanism has a length of about 0.06 inch. 
     
     
       6. The device of  claim 1 , wherein the proximal section of the distal portion of each tine of the fixation mechanism has a length of about 0.1 inch. 
     
     
       7. The device of  claim 1 , wherein, when in a deployed configuration, the second pre-formed curvature of the hook section of the distal portion of each tine of the fixation mechanism is defined by a radius, when un-deformed, being about 0.05 inch. 
     
     
       8. The device of  claim 1 , wherein, when in a deployed configuration, the second pre-formed curvature of the hook section of the distal portion of each tine of the fixation mechanism is defined by two radii and a straight length extending therebetween. 
     
     
       9. The device of  claim 1 , wherein the elastically deformable material comprises a nickel-titanium alloy. 
     
     
       10. The device of  claim 1 , wherein a length from the second pre-formed curvature to the distal free end is configured such that, when the tine is released from the spring-loaded position to the pre-formed position with the free distal end adjacent to the pectinate muscle of a heart, the tine penetrates the pectinate muscle without penetrating the tissue layer of heart beneath the pectinate muscle. 
     
     
       11. The device of  claim 1 , wherein the relatively straight line of the proximal section of the distal portion of each tine of the plurality of tines and the longitudinal axis of the device body define an acute angle within a range from about 30 degrees and about 50 degrees. 
     
     
       12. The device of  claim 11 , wherein the acute angle is about 45 degrees. 
     
     
       13. The device of  claim 1 , wherein, when in the deployed configuration, the second pre-formed curvature of the hook section of the distal portion of each tine of the plurality of tines orients the corresponding tip section to enclose, with the corresponding proximal section, an angle of from about 70 degrees to about 120 degrees. 
     
     
       14. The device of  claim 13 , wherein the angle is no less than about 90 degrees. 
     
     
       15. The device of  claim 1 ,
 wherein the relatively straight line of the proximal section of the distal portion of each tine of the plurality of tines intersects the longitudinal axis of the device body at an acute angle within a range from about 30 degrees and about 50 degrees, and 
 wherein, when in a deployed configuration, the second pre-formed curvature of the hook section of the distal portion of each tine of the plurality of tines orients the corresponding tip section to enclose, with the corresponding proximal section, an angle of from about 70 degrees to about 120 degrees. 
 
     
     
       16. The device of  claim 1 , wherein each tine of the plurality of tines is configured such that, when released from a spring-loaded position to a pre-formed position with the free distal end adjacent to a pectinate muscle of a heart, each tine penetrates the pectinate muscle without penetrating a tissue layer of heart beneath the pectinate muscle. 
     
     
       17. An implantable medical device (IMD) including a device body extending along a longitudinal axis from a proximal end to a distal end, an electrode mounted in proximity to the distal end of the device body, and a fixation mechanism comprising a plurality of tines formed from an elastically deformable material, each tine of the plurality of tines being fixedly mounted and spaced from one another around a perimeter of the distal end of the device body, wherein each tine of the plurality of tines, when in a deployed configuration, comprises:
 a proximal portion fixedly attached to the device body and extending from the device body in a first direction, wherein the proximal portion comprises a first pre-formed curvature; 
 a distal portion comprising a proximal section extending from the first pre-formed curvature, the distal portion comprising a hook section extending from the proximal section, and the hook section defining a second pre-formed curvature; 
 a tip section extending from the hook section to a free distal end, wherein the hook section is configured to orient the free distal end to enclose with the proximal section an angle within a range from about 70 degrees to about 120 degrees. 
 
     
     
       18. The device of  claim 17 , wherein the proximal section defines a relatively straight line which intersects the longitudinal axis at an acute angle within a range from about 30 degrees and about 50 degrees. 
     
     
       19. The device of  claim 17 , wherein the angle is greater than or equal to about 90 degrees. 
     
     
       20. The device of  claim 17 , wherein the elastically deformable material comprises a nickel-titanium alloy. 
     
     
       21. An implantable medical device (IMD) defining a longitudinal axis extending between a proximal end and a distal end, the IMD comprising:
 an electrode mounted in proximity to the distal end; 
 a fixation mechanism comprising a plurality of tines formed from an elastically deformable material, each tine of the plurality of tines being fixedly mounted and spaced from one another around a perimeter of the distal end of the IMD, and each tine of the plurality of tines, wherein, when in a deployed configuration, each tine of the plurality of tines comprises:
 a proximal portion fixedly attached to the IMD and extending therefrom, wherein the proximal portion comprises a first pre-formed curvature; 
 a distal portion comprising a proximal section extending from the first pre-formed curvature and comprising a hook section extending from the proximal section, the hook section defining a second pre-formed curvature, 
 wherein the proximal section extends along a relatively straight line that intersects the longitudinal axis distal to the distal end of the IMD, the relatively straight line intersecting the longitudinal axis at an acute first angle within a range from about 30 degrees and about 50 degrees; and 
 a tip section extending from the hook section to a free distal end. 
 
 
     
     
       22. The system of  claim 21 , wherein each tine of the plurality of tines is configured such that, upon deployment of the tip section thereof out from a distal opening of a delivery tool, each tip section rotates away from the longitudinal axis to extend at a second angle that approaches 90 degrees relative to the longitudinal axis. 
     
     
       23. The system of  claim 21 , wherein the second angle is greater than or equal to about 90 degrees. 
     
     
       24. The system of  claim 21 , wherein, when in the deployed configuration:
 the first pre-formed curvature of each tine of the plurality of tines is spaced distally from the distal end of the device body; and 
 the electrode is flush with, or spaced distally from the first pre-formed curvature by a distance less than or equal to about 2 mm. 
 
     
     
       25. The device of  claim 1 , wherein the first pre-formed curvature is defined by a first radius and the second pre-formed curvature is defined by a second radius less than the first radius. 
     
     
       26. The device of  claim 1 , wherein at least one of a position of the first pre-formed curvature, a position of the second pre-formed curvature, a radius of curvature of the first pre-formed curvature, or a radius of curvature of the second pre-formed curvature is configured such that, when the tine is released from the spring-loaded position to the pre-formed position with the free distal end adjacent to the pectinate muscle of a heart, the tine penetrates the pectinate muscle without penetrating the tissue layer of heart beneath the pectinate muscle. 
     
     
       27. A medical device system including an implantable medical device (IMD), the IMD comprising:
 a device body extending along a longitudinal axis from a proximal end to a distal end; 
 an electrode mounted in proximity to the distal end of the device body; and 
 a fixation mechanism comprising a plurality of tines formed from an elastically deformable material, each tine of the plurality of tines being fixedly mounted and spaced from one another around a perimeter of the distal end of the device body, wherein each tine of the plurality of tines, when in a deployed configuration, comprises: 
 a proximal portion fixedly attached to the device body and extending therefrom; 
 a distal portion comprising a proximal section extending from the first pre-formed curvature, the distal portion comprising a hook section extending from the proximal section, and the hook section defining a second pre-formed curvature, 
 wherein each tine of the plurality of tines is configured such that, upon deployment of the tip section thereof out from a distal opening of a delivery tool, each tip section rotates away from the longitudinal axis to extend at an angle that approaches 90 degrees relative to the longitudinal axis; and 
 wherein, when in a deployed configuration, an intersection between the proximal portion and the distal portion of each tine of the plurality of tines is spaced distally from the distal end of the device body, and 
 wherein the electrode is flush with, or spaced distally from the intersection between the proximal portion and the distal portion by a distance less than or equal to about 2 mm; and 
 a tip section extending from the hook section to a free distal end. 
 
     
     
       28. The medical device system of  claim 27 , further comprising the delivery tool, wherein the delivery tool comprises a tubular sidewall that defines a lumen having the distal opening, wherein the IMD may be loaded into the lumen and deployed through the distal opening, and wherein, when loaded into the lumen of the delivery tool in an undeployed configuration, the free distal end of each tine of the plurality of tines is configured to engage the tubular sidewall to hold each tine of the plurality of tines in a spring-loaded condition.